PHP reference

array_unique

Removes duplicate values from an array.

Available since: PHP 4

Syntax

array_unique(array $array, int $flags = SORT_STRING): array

Parameter	Type	Description
$array	array	The source array.
$flags	int	How values are compared. By default they are compared as strings.

arrayThe array without duplicates. The first occurrence of each value is kept, and keys are preserved.

The keys of the remaining elements are preserved:

<?php
 
print_r(array_unique([1, 2, 2, 3, 1]));

Output:

Array
(
    [0] => 1
    [1] => 2
    [3] => 3
)

A plain list without duplicates:

<?php
 
echo implode(', ', array_values(array_unique(['b', 'a', 'b', 'c', 'a'])));

Output:

b, a, c

Values are compared loosely, as strings: the number 1 and the string '1' count as duplicates.

Arrays — Lists and associative arrays in PHP — creating, changing, iterating and useful functions.